KR20080074962A - Laminated piezoelectric element and process for producing the same - Google Patents

Abstract

A laminated piezoelectric element having basis body (10) composed of, alternately superimposed one upon another, internal electrode layers (21,22) and piezoelectric ceramic layers (11), wherein while the internal electrode layers (21,22) are composed mainly of Cu, the piezoelectric ceramic layers (11) are composed mainly of a composite oxide represented by the formula Pb(Ti,Zr)O3, and wherein a metal oxide containing Nb, Sb, Ta or W being a metal element of at least either valence 5 or valence 6 (Nb2O5, Sb2O5, Ta2O5 or WO3) is contained in the piezoelectric ceramic layers (11) so that the concentration thereof is decreased as the distance from the internal electrode layers (21,22) is increased. Thus, there can be realized a laminated piezoelectric element that even when the internal electrode is composed mainly of Cu, permits low-temperature firing while ensuring satisfactory piezoelectric constant.

Description

Laminated piezoelectric element and its manufacturing method {LAMINATED PIEZOELECTRIC ELEMENT AND PROCESS FOR PRODUCING THE SAME}

The present invention relates to a laminated piezoelectric element such as a piezoelectric actuator, a piezoelectric resonator, a piezoelectric filter, and a manufacturing method thereof.

PZT-based piezoelectric ceramics mainly composed of Pb (Ti, Zr) O ₃ (hereinafter referred to as "PZT") as a representative piezoelectric ceramics used in stacked piezoelectric elements such as piezoelectric actuators, piezoelectric resonators and piezoelectric filters are widely known. have.

In addition, as a multilayer piezoelectric element using PZT-based piezoelectric ceramics, an internal electrode layer made of Ag-Pd alloy and a ceramic layer made of PZT-based piezoelectric ceramic are alternately laminated and fired at the same time. Since Pd is expensive, the internal electrode material As a result, research and development of laminated piezoelectric elements using inexpensive Cu have been actively performed.

For example, Patent Document 1 discloses a multilayer piezoelectric element using PZT-based piezoelectric ceramics whose internal electrode layer contains Cu as a main component.

In this Patent Document 1, a perovskite oxide comprising Cu as a main component and piezoelectric ceramics, piezoelectric ceramics represented by the general formula ABO ₃ , containing Pb at A site and Zr and Ti at B site. When the main component is composed of an acceptor element composed of a divalent metal element and a donor element composed of a pentavalent metal element, the molar amount of the acceptor element is a mole and the total molar amount of the donor element is b mole. , A multilayer piezoelectric element with 0.42 < a / b < 0.5 is disclosed.

When firing the electrodes and the piezoelectric ceramic mainly composed of Cu at the same time, Cu of the electrode is diffused to act as the acceptor element divalent billion in the state of Cu ^{+ 2} in the piezoelectric ceramic. For this reason, in the laminated piezoelectric element of Patent Literature 1, the B-site of the piezoelectric ceramic composition is made into donor excess so that the total molar amount (a) of the acceptor element and the total molar amount (b) of the donor element are 0.42 <a / b <0.5. As a result, the average of B sites due to the diffusion of Cu cancels the decrease in the number, thereby making it possible to suppress the decrease in the piezoelectric constant.

[Patent Document 1] International Publication WO2005 / 071769 Pamphlet

In the stacked piezoelectric element described in Patent Literature 1, the composition of the PZT-based piezoelectric ceramics causes the B-site to be excessively donor, so that even when the internal electrode has Cu as a main component, the piezoelectric constant almost equal to that when the internal electrode of Ag-Pd alloy is used Getting

However, when the B site is excessively donated, the sintering property is lowered, so that baking at a relatively high temperature is required. For example, in the laminated piezoelectric element of Patent Document 1, the firing temperature is set to 1000 ° C. (Patent Document 1, paragraph No. ] Reference).

On the other hand, since the melting point of Cu is about 1050 ° C, the firing temperature of 1000 ° C is close to the melting point, so it is preferable to lower the firing temperature. In addition, since the diffusion amount of Cu can also be suppressed by lowering the firing temperature, it is preferable that the firing temperature is also lower in this respect. In addition, if the firing temperature is lowered, the energy required for firing may also be small, which saves fuel and power and reduces manufacturing costs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a laminated piezoelectric element and a method for manufacturing the same, which can be obtained by low-temperature firing while ensuring a sufficient piezoelectric constant even when the internal electrode mainly contains Cu.

The present inventors earnestly studied to achieve the above object, and the metal oxide is contained in the piezoelectric ceramics so that the concentration decreases as it is separated from the internal electrode layer, so that the average of the B site of the piezoelectric ceramic composition due to the diffusion of Cu is increased. The fall of the number can be compensated for the charge, thereby obtaining the knowledge that a sufficient piezoelectric constant can be obtained without making the B-site composition of the piezoelectric ceramics excessively donor. In addition, since there is no need for excess donor, the sinterability can be improved, and a desired laminated piezoelectric element can be obtained by low temperature firing.

That is, the stacked piezoelectric element according to the present invention is a stacked piezoelectric element having an element in which an internal electrode layer and a piezoelectric ceramic layer are alternately stacked, wherein the internal electrode layer contains Cu as a main component, and the piezoelectric ceramic layer is formed of Pb (Ti, It is contained in the piezoelectric ceramic layer such that the metal oxide containing Zn) O ₃ as a main component and the metal oxide containing at least one of pentavalent and hexavalent ones is separated from the inner electrode layer so as to have a lower concentration. It is characterized by.

In the multilayer piezoelectric element of the present invention, the metal element is at least one member selected from Nb, Sb, Ta, and W.

In addition, a method of manufacturing a stacked piezoelectric element according to the present invention includes a lamination process of manufacturing a laminate in which internal electrode patterns and piezoelectric ceramic green sheets are alternately stacked, and firing the laminate to alternately laminate an internal electrode layer and a piezoelectric ceramic layer. A method of manufacturing a laminated piezoelectric element comprising a firing process for fabricating a compacted body, wherein the piezoelectric ceramic green sheet has a composite oxide represented by Pb (Ti, Zr) O ₃ as a main component, and the internal electrode pattern contains Cu. A conductive element and a metal element having a number of at least one of pentavalent and hexavalent, wherein the metal element is formed in the piezoelectric ceramic layer from the inner electrode layer in the form of a metal oxide in the firing step; As the separation from the internal electrode layer is characterized in that the diffusion to lower the concentration.

In addition, the method for manufacturing a laminated piezoelectric element of the present invention is characterized in that the metal element is at least one selected from Nb, Sb, Ta, and W.

In addition, the method for manufacturing a multilayer piezoelectric element of the present invention is characterized in that the metal oxide is represented by any one of Nb ₂ O ₅ , Sb ₂ O ₅ , Ta ₂ O _5, and WO ₃ .

Moreover, the manufacturing method of the laminated piezoelectric element of this invention is characterized in that content of the said metal oxide is less than 40.0 weight% with respect to the content total of the said electroconductive powder and the said metal oxide.

Effect of the Invention

According to the stacked piezoelectric element of the present invention, the piezoelectric element is formed such that the metal oxide containing at least one of the five and six valent metal elements (Nb, Sb, Ta, W, etc.) is lowered as the metal oxide is separated from the internal electrode layer. Since it is contained in the ceramic layer, charge reduction of the average number due to the diffusion of Cu can be compensated for by the metal oxide, so that a good piezoelectric constant can be ensured even when the charge is excessive and the charge compensation is not performed. In addition, since the B site does not need to be excessively donor, the sintering property can be improved and further low temperature firing is possible. In the vicinity of the internal electrode having a large decrease in the average number due to diffusion of Cu, charge compensation can be effectively performed with the metal oxide, while the above-mentioned space is separated from the internal electrode layer in which the average decrease due to diffusion of Cu is not significant. Since the concentration of the metal oxide is low, the metal oxide is not excessively distributed in the piezoelectric ceramics, whereby the sintering deterioration can be suppressed, thereby being suitable for low temperature firing.

In addition, according to the method for manufacturing a laminated piezoelectric element of the present invention, the internal electrode pattern includes a conductive powder containing Cu and a metal element (Nb, Sb, Ta, W, etc.) having at least one of valences of pentavalent and hexavalent. In the firing step, the metal element is formed in the piezoelectric ceramic layer from the inner electrode layer in the form of a metal oxide such as Nb ₂ O ₅ , Sb ₂ O ₅ , Ta ₂ O ₅ , WO _3, and the like. As the metal oxide diffuses away from the electrode layer so as to have a low concentration, a concentration gradient of the metal oxide is formed in the piezoelectric ceramic layer. Therefore, it is possible to easily manufacture a laminated piezoelectric element whose concentration decreases as the metal oxide is separated from the internal electrode layer in the piezoelectric ceramic layer, and thus a laminated piezoelectric element capable of obtaining a sufficient piezoelectric constant even at low temperature firing can be manufactured.

In addition, since the content of the metal oxide is less than 40.0% by weight based on the total content of the conductive powder and the metal oxide, the connection between the internal electrode layer and the external electrode does not decrease and a high quality multilayer piezoelectric element having excellent reliability can be obtained.

1 is a cross-sectional view showing a laminated piezoelectric element of the present invention.

FIG. 2 is a diagram showing the relationship between the content of Nb ₂ O ₅ in the internal electrode patterns and the piezoelectric constant d ₃₃ .

Figure 3 is a view showing the relationship between the content and the piezoelectric constant (d ₃₃₎ of WO ₃ in the electrode pattern.

<Description of the code>

10 element body 11: piezoelectric ceramic layer

21,22: internal electrode layer

Next, the best form for implementing this invention is demonstrated, referring an accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows one Embodiment of the laminated piezoelectric element of this invention.

The stacked piezoelectric element is composed of a body 10 having a piezoelectric ceramic layer 11 and internal electrode layers 21 and 22 alternately stacked with external electrodes 31 and 32 formed on the surface of the body 10. The internal electrode layer 21 connected to the external electrode 31 and the internal electrode layer 22 connected to the other external electrode 32 are alternately arranged. The multilayer piezoelectric element is configured such that an electric field is generated between the internal electrode layers 21 and 22 by applying a voltage between the external electrodes 31 and 32 so that the piezoelectric ceramic layer 11 is stretched.

The internal electrode layers 21 and 22 contain a conductive powder containing Cu as a main component and a metal oxide containing a metal element having at least one of valences of pentavalent and hexavalent. Here, Nb, Sb, Ta can be used as the pentavalent metal element, and W (tungsten) can be used as the pentavalent metal element. Therefore, the metal oxide is contained in the internal electrode layers 21 and 22 in the form of Nb ₂ O ₅ , Sb ₂ O ₅ , Ta ₂ O _5, or WO ₃ , for example.

As described above, the internal electrode layers 21 and 22 contain Cu as a main component as the conductive powder, and preferably contain Ni as a subcomponent. Since melting | fusing point of Ni is 1450 degreeC as high as melting | fusing point of Cu is 1050 degreeC, melting | fusing point of internal electrode layers 21 and 22 raises by containing Ni, and diffusion of Cu is suppressed. In addition, since Ni is more easily oxidized than Cu, oxidation of Cu is suppressed, and diffusion of Cu is also suppressed by this. Moreover, when it contains Ni as a subcomponent, it is preferable that the content rate of Cu and Ni is 85: 15-70: 30 by weight ratio. This is because the effect of suppressing oxidation and diffusion of Cu when the content ratio of Ni is 15% by weight or more is high, and thus the reduction of the piezoelectric constant due to the diffusion of Cu can be effectively suppressed. However, if the content of Ni exceeds 30% by weight, the content of Cu is excessively low, which may cause breakage of the internal electrode layers 21 and 22, which is not preferable.

In addition, when Ni is contained in the internal electrode layers 21 and 22, most of Ni exists as NiO. When the internal electrode layers 21 and 22 contain Ni, it is preferable that Ni is also included in the composition of the piezoelectric ceramic layer 11. This is because Ni is included in the composition of the piezoelectric ceramic layer 11 to suppress diffusion of NiO from the internal electrode layers 21 and 22 to the piezoelectric ceramic layer 11.

The piezoelectric ceramic layer 11 has a PZT-based composite oxide having a perovskite structure represented by the general formula ABO ₃ as the main component, and is formed by PZT (Pb (Ti, Zr) 0 ₃ ) alone. For example, a composition in which a part of B site is substituted with Ni, Nb, Zn or the like may be employed by solidifying PZT with another perovskite complex oxide such as Pb (Ni, Nb) 0 ₃ or Pb (Zn, Nb) 0 ₃ .

In the PZT-based composite oxide, a part of the B-site is a combination of various cations, for example, a combination of monovalent and pentavalent cations, a combination of divalent and pentavalent cations, and a combination of trivalent and pentavalent cations. The composition substituted by the combination or the combination of trivalent cation and hexavalent cation may be sufficient. Here, Na, K can be used as the monovalent cation, and Ni, Zn, Co, Mg, Mn, Fe, Cr, Cu can be used as the divalent cation. Fe, In, Sc, Yb can be used as the trivalent cation, Nb, Sb, Ta, V can be used as the pentavalent cation, and W can be used as the hexavalent cation.

The average valence number of B site becomes tetravalent or its vicinity, specifically, 3.95 or more and 4.05 or less are preferable. This is because when the average number of B sites is less than 3.95, the piezoelectricity may be deteriorated due to excessive diffusion of CuO from the internal electrode side. On the other hand, when the average number of B sites is over 4.05, the sinterability may be deteriorated, and the baking at low temperature may be difficult.

Pb constituting the A site of the PZT-based composite oxide may also be substituted with Ba, Sr, Ca, which is a divalent cation, or La, Y, Bi, Nd, which is a trivalent cation, if necessary. In this case, it is preferable that the substitution ratio by these elements shall be 5 mol% or less. This is because if the substitution ratio exceeds 5 mol%, the sinterability may be reduced.

The average number of A sites becomes divalent or its vicinity, and specifically 1.94 or more and 2.05 or less are preferable. This is because if the average number of A sites is less than 1.94 or more than 2.05, the sintering property may be lowered and the baking at low temperature may be difficult.

The piezoelectric ceramic layer 11 contains a metal oxide containing a pentavalent or hexavalent metal element, the concentration of which is high in the vicinity of the inner electrode layers 21 and 22 and distant from the inner electrode layers 21 and 22. It is supposed to fall accordingly. This is because the metal oxides such as Nb ₂ O ₅ , Sb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and the like contained in the internal electrode layers 21 and 22 are formed from the piezoelectric ceramic layers from the internal electrode side 21 and 22 during firing. It is formed by diffusing to 11) side. As the concentration of the metal oxide having a pentavalent or hexavalent metal element is separated from the internal electrode layers 21 and 22 in this manner, the piezoelectric ceramic layer 11 is reduced in the average number of B sites due to Cu diffusion. Charge compensation can be performed with the above-mentioned pentavalent or hexavalent metal oxide even if the donor element in the layer is not excessively larger than the stoichiometric composition.

As described above, charge compensation of a decrease in the number of B sites due to diffusion of Cu with a metal oxide eliminates the need for excessive donor charge compensation, thereby making it possible to obtain a laminated piezoelectric element having a sufficient piezoelectric constant in low-temperature firing. In addition, in the vicinity of the internal electrodes 21 and 22 where the average number decreases due to the diffusion of Cu, charge compensation can be effectively performed, while the internal electrode layer 21 in which the average number decreases due to the diffusion of Cu is not so large. Since the pentavalent or hexavalent metal oxide does not exist more than necessary at the point separated from (22), it is not necessary to increase the content of the pentavalent or hexavalent metal oxide more than necessary, and the sintering deterioration can be suppressed in this respect as well. The baking at low temperature is possible.

In addition, this invention does not exclude the case where the composition of a piezoelectric ceramic layer makes excess donor. That is, even when the piezoelectric ceramic layer is made of an excessive donor composition, by applying the present invention, it is possible to compensate for the decrease in the average value due to Cu diffusion without excessively making the donor excessive.

The external electrodes 31 and 32 are made of Cu, Ag-Pd alloy, or the like, and are formed by performing baking treatment on the surface of the body 10.

Next, the manufacturing method of this laminated piezoelectric element is demonstrated.

First, small raw materials such as Pb ₃ O ₄ , TiO ₂ , ZrO ₂ , NiO, ZnO, Nb ₂ O _5, etc. are prepared, mixed at a predetermined ratio, pulverized, and calcined. Calcination powder of piezoelectric ceramics is obtained. This calcined powder is kneaded with a binder or a plasticizer to obtain a piezoelectric ceramic green sheet by a doctor blade method.

In addition, according to the Cu powder, a metal oxide, a 5 or containing a hexavalent metal element, specifically, for example, Nb ₂ O _5, at least one of Sb ₂ O _5, Ta ₂ O _5, WO ₃ species, is also required The electrically conductive paste for internal electrodes containing Ni powder is produced. In addition, when Ni powder is contained in an electrically conductive paste, it mix | blends so that the content rate of Cu powder and Ni powder may be 70: 30-85: 15 by weight ratio. Moreover, it is preferable to make content of a metal oxide into less than 40.0 weight% with respect to the total content of electroconductive powder and a metal oxide (henceforth both these "solid content"). This is because the content of Cu in the internal electrode layers 21 and 22 decreases when the content of the metal oxide exceeds 40.0% by weight based on the total content of the total solids, so that between the internal electrode layers 21 and 22 and the external electrodes 31 and 32. This is because a connection failure may occur.

Next, the conductive paste is printed on a piezoelectric ceramic green sheet to form an internal electrode pattern. Thereafter, a piezoelectric ceramic green sheet having an internal electrode pattern formed thereon and a piezoelectric ceramic green sheet having no internal electrode pattern formed thereon are laminated in a predetermined order to produce a laminate.

Subsequently, the laminated body is baked at a baking temperature of 950-1000 degreeC for about 5 to 10 hours, and the body 10 is produced. Moreover, as a baking atmosphere, the equilibrium oxygen partial pressure of Pb-PbO and Cu-CuO is suppressed from the viewpoint which suppresses the reduction of Pb contained in the piezoelectric ceramic layer 11, suppressing oxidation of Cu which is a main component of the internal electrode layers 21 and 22. It is preferable to set it as the atmosphere of oxygen partial pressure between the equilibrium oxygen partial pressure of

The pentavalent or hexavalent metal oxide contained in the internal electrode pattern diffuses in the piezoelectric ceramic layer 11 so as to decrease in concentration as it is separated from the internal electrode layers 21 and 22 during the firing process. As a result, the average number of B sites due to Cu diffused from the internal electrode layer to the piezoelectric ceramic layer during the sintering treatment is reduced in the number of charges, and the reduction of the characteristics of the piezoelectric ceramics is suppressed even when the B sites are not excessively donor. It becomes possible.

Next, an external electrode is formed on the surface of the obtained body by baking a conductive paste containing Cu or Ag-Pd alloy as a main component. Polarization is applied by applying a predetermined voltage in oil, whereby a multilayer piezoelectric element is manufactured.

In the present embodiment, since the metal oxide is diffused from the internal electrode layers 21 and 22 to the piezoelectric ceramics 11 as described above, the composition of the piezoelectric ceramics layer 11 does not need to be excessively donor and low-temperature firing is possible. Become.

In addition, this invention is not limited to the said embodiment. In the above embodiment, the metal oxide containing a pentavalent or hexavalent metal element is contained in the internal electrode pattern. If the metal oxide is distributed in the piezoelectric ceramic layer 11 in the form of a metal oxide, the metal oxide is formed in the internal electrode pattern. It does not need to be contained. That is, in the internal electrode pattern, for example, it may be contained as a single metal, or may be contained as a compound such as carbonate, hydroxide, or organic compound. In the case where the pentavalent or hexavalent metal element is contained in the conductive paste for the internal electrode layer in a form other than the metal oxide, it is preferable to add so as to be less than 40.0% by weight in terms of the metal oxide.

In addition, the present invention can obtain a sufficient piezoelectric constant by low-temperature firing without making the B-site composition of the piezoelectric ceramics excessively donor. However, the B-site composition does not exclude that the donor excess is excessive, It is acceptable to make excess donor in the range which does not cause a sintering fall.

In the piezoelectric ceramic layer of the metal oxide diffused from the internal electrode layer side to the piezoelectric ceramic layer, any form of the metal oxide may be dissolved in crystal grain boundaries, triple crystals, or complex oxides having a perovskite structure. It may be the case.

Next, embodiments of the present invention will be described in detail.

(Example 1)

First, each of powders of Pb ₃ O ₄ , TiO ₂ , ZrO ₂ , NiO, ZnO, and Nb ₂ O ₅ was prepared as a raw material of piezoelectric ceramics and weighed so as to have a composition shown in the following formula (1).

_{pb {(Ni 1/3 Nb} 2/3) 0.1 (Zn 1/3 Nb 2/3) 0.1 Ti 0 .42 Zr 0 .38) 0 3 ... (One)

The calcined portion of the piezoelectric ceramics was obtained by mixing the weighed small raw materials and calcining at 880 ° C. after 16 hours of grinding. This calcined powder was kneaded with a binder or a plasticizer to obtain a piezoelectric ceramic green sheet having a thickness of 120 µm by the doctor blade method.

Next, as a conductive powder to prepare a Cu powder and Ni powder, preparing a Nb ₂ O ₅ as a metal oxide containing a pentavalent metal element.

And, Cu powder and Ni content ratio is 85: 15, total solid weight ratio of the powder (Nb ₂ O _5, Cu powder and Ni powder) Nb ₂ O ₅ content is 0 to 40% by weight thereof so that the Cu powder for , Ni powder and Nb ₂ O ₅ were weighed. Subsequently, a binder or the like was added to the weighing material, followed by mixing and kneading in an organic vehicle to prepare a conductive paste for internal electrodes.

Next, the conductive paste was screen printed on a piezoelectric ceramic green sheet to form an internal electrode pattern. Thereafter, the piezoelectric ceramic green sheet on which the internal electrode pattern was formed and the plain piezoelectric ceramic green sheet on which the internal electrode pattern was not formed were laminated in a predetermined order, and then pressed into a press to have 80 layers of internal electrode patterns. The laminated body was produced.

After the binder was subjected to the binder removal treatment, the body was calcined for 5 hours in an atmosphere of oxygen partial pressure between the equilibrium oxygen partial pressure of Pb-PbO and the equilibrium oxygen partial pressure of Cu-CuO. In addition, the baking temperature was set to 950 degreeC, 975 degreeC, and 1000 degreeC, and the several types of elementary bodies were obtained.

Next, an external electrode was formed by baking an electrically conductive paste for external electrodes containing Cu as a main component on the surface of the body. Subsequently, it polarized in the electric field strength of 3 kPa / mm in 80 degreeC silicone oil, and produced the laminated piezoelectric element of sample numbers 1a-9c by this. In addition, the dimension of the laminated piezoelectric element was 6 mm long, 6 mm wide, and 8 mm high.

Subsequently, an electric field strength of 2 Hz / mm is applied to each obtained sample by a triangular wave of frequency 0.1 Hz, and the strain in the thickness direction at this time is measured by an inductive probe and a differential transformer. The piezoelectric constant (d ₃₃ ) was calculated by dividing the strain by the electric field.

In addition, the contents (concentrations) of Nb ₂ O ₅ and CuO were measured at four places in the piezoelectric ceramic layers having different distances from the internal electrode layers for each of the samples of Sample Nos. 1b, 2b, and 5b. That is, the thickness of the piezoelectric ceramic green sheet is 120 μm as described above, and the thickness of the piezoelectric ceramic layer is shrunk to about 100 μm by firing, and 3 μm, 6 μm, 20 μm, and 50 μm from the internal electrode layers, respectively. The concentrations (contents) of Nb ₂ O ₅ and CuO in four of the separated piezoelectric ceramics were measured using WDX (wavelength dispersion X-ray spectroscopy).

Table 1 shows the Nb ₂ O ₅ content, firing temperature and piezoelectric constant (d ₃₃ ) for all solids in the internal electrode patterns of each sample. Table 2 shows Nb ₂ O ₅ at each measurement point in the piezoelectric ceramic layer. And the concentration of CuO.

Also, WDX roneun can not be determined by the oxidation number of the atoms, some of the Cu is likely to be spread as the Cu ₂ O. Therefore, Table 2 of the CuO concentration is strictly represents the total amount of CuO and Cu ₂ O concentration each.

* Is outside the scope of the present invention

* Is outside the scope of the present invention

As is apparent from Table 1, the samples Nos. 1a to 1c obtained only a low value of the piezoelectric constant d ₃₃ at 410 to 440 pm / V even when the firing temperatures were different.

On the other hand, the sample numbers 2a to 8c showed that the piezoelectric constants d ₃₃ were 530 to 750 pm / V, and the piezoelectric constants d ₃₃ were improved compared to the sample numbers 1a to 1c.

As apparent from Table 2, Sample No. 1b does not contain Nb ₂ O ₅ in the internal electrode pattern, but the Nb component is contained in the piezoelectric ceramic composition as shown in the above formula (1). It was found that the Nb ₂ O ₅ contained almost uniformly in the piezoelectric ceramic layer.

On the other hand, since the sample numbers 2b and 5b contained Nb ₂ O ₅ in the internal electrode pattern, the Nb ₂ O ₅ diffused from the internal electrode layer side into the piezoelectric ceramic layer during the firing process, so that the concentration of Nb ₂ O ₅ was increased in the internal electrode layer. It is relatively high in the vicinity and is distributed in the piezoelectric ceramics so as to become lower as they are separated from the internal electrode layers.

That is, Cu in the internal electrode pattern diffuses in the piezoelectric ceramic layer from the internal electrode layer side during the firing process. In the case where Nb ₂ O ₅ is not included in the internal electrode pattern, since the Nb ₂ O ₅ does not diffuse in the piezoelectric ceramic layer from the internal electrode layer side, the piezoelectric constant (d ₃₃ ) can be improved due to the diffusion of Cu. none.

On the other hand if it contains Nb ₂ O ₅ in the electrode pattern is, Nb ₂ O ₅ is because the diffusion in the piezoelectric ceramic layer from the internal electrode layer side as described above may B average cost of the site the composition piezoelectric ceramic due to diffusion of Cu It was found that the decrease in was charge-compensated by Nb ₂ O ₅ , whereby a sufficient piezoelectric constant could be ensured while enabling low-temperature firing.

Further, as is apparent from the comparison of the samples a to c of Sample Nos. 2 to 8, as the firing temperature is lowered, the piezoelectric constant (d ₃₃ ) is improved to obtain a better piezoelectric constant (d ₃₃ ) at the firing temperature of 950 ° C. I could see that.

However, in Sample Nos. 9a to 9c, the content of Nb ₂ O ₅ with respect to the total solids in the internal electrode pattern was 40.0% by weight, so the piezoelectric constant d ₃₃ could not be obtained. This is because, when the content of Nb ₂ O ₅ is excessively high, the content of Cu decreases, resulting in a poor connection between the external electrode and the internal electrode layer. Therefore, in the case of the laminated piezoelectric element having the same shape as in the present embodiment, it was found that the content of Nb ₂ O _{5 relative} to the total solid content is less than 40.0 wt%.

2 is a diagram showing the relationship between the content of Nb ₂ O ₅ and the piezoelectric constant d ₃₃ , where the horizontal axis represents the content (% by weight) of Nb ₂ O ₅ and the vertical axis represents the piezoelectric constant d ₃₃ (pm / V). ◆ The mark indicates the firing temperature of 1000 ℃, the mark shows the firing temperature of 975 ℃, and the mark indicates the firing temperature of 950 ℃.

As apparent from Table 1 and FIG. 2, it was confirmed that the piezoelectric constant (d ₃₃ ) also tended to increase as the Nb ₂ O ₅ content was increased and the firing temperature was lower.

(Example 2)

A laminated piezoelectric element of Sample Nos. 11a to 19c was fabricated in the same manner and procedure as in Example 1, using WO ₃ containing a hexavalent metal element instead of Nb ₂ O ₅ as a metal oxide contained in the internal electrode pattern. .

Subsequently, the piezoelectric constant d ₃₃ was calculated in the same method and procedure as in Example 1 for Sample Nos. 11a to 19c, and the concentrations of WO ₃ and CuO for each of Sample Nos. 1 lb, 12b, and 15b ( Content) was measured using WDX (wavelength dispersion X-ray spectroscopy).

Table 3 shows the content of WO ₃ , firing temperature and piezoelectric constant (d ₃₃ ) for all solids in the internal electrode patterns of each sample. Table 4 shows the concentrations of WO ₃ and CuO at each measurement point in the piezoelectric ceramics. It is shown.

* Is outside the scope of the present invention

* Is outside the scope of the present invention

As is apparent from Table 3, samples Nos. 11a to 11c obtained only low values of the piezoelectric constant d ₃₃ at 410 to 440 pm / V even when the firing temperatures were different.

On the other hand, the sample numbers 12a to 18c had a high piezoelectric constant (d ₃₃ ) of 460 to 765 pm / V, indicating that the piezoelectric constant (d ₃₃ ) was improved compared to the sample numbers 11a to 11c.

In addition, as apparent from Table 4, sample No. 1lb because does not contain a WO ₃ in the piezoelectric ceramic (see the above composition formula (1)), and while the electrode pattern does not contain a WO ₃ WO ₃ is not at all detected Did.

In contrast sample No. 12b, 15b because the WO ₃ is contained in the internal electrode pattern, by diffusing into the piezoelectric ceramic layer from the internal electrode layer side in the WO ₃ is fired concentration of WO ₃ is high and relatively in the vicinity of the internal electrode layers, internal It is distributed in piezoelectric ceramics so as to be lowered as it is separated from the electrode layer.

That is, Cu in the internal electrode pattern diffuses in the piezoelectric ceramic layer from the internal electrode layer side during the firing process. And it does not include WO ₃ in the electrode pattern is, the WO ₃ does not diffuse into the piezoelectric ceramic layer from the internal electrode layer side can not be due to diffusion of Cu to improve the piezoelectric constant (d _33).

On the other hand, when WO ₃ is included in the internal electrode pattern, as described above, since WO ₃ diffuses into the piezoelectric ceramic layer from the internal electrode layer side, the average number of B sites in the piezoelectric ceramic composition due to diffusion of Cu decreases. It was found that charge compensation was performed by WO ₃ , whereby a sufficient piezoelectric constant could be ensured while enabling low-temperature firing.

In addition, as is apparent from the comparison of the samples a to c of Sample Nos. 12 to 18, the piezoelectric constant (d ₃₃ ) is improved as the firing temperature is lowered as in (Example 1), and the piezoelectric is better at the firing temperature of 950 ° C. It was found that the constant d ₃₃ was obtained.

However, Sample Nos. 19a to 19c have a high content of WO ₃ of 40.0 wt% with respect to the total solids in the internal electrode patterns, which is why the piezoelectric constant d is the same as that described in Sample Nos. 9a to 9c of (Example 1). ₃₃ ) could not be obtained.

3 is a diagram showing the relationship between the content of WO ₃ and the piezoelectric constant d ₃₃ , where the horizontal axis is the content (% by weight) of WO ₃ and the vertical axis is the piezoelectric constant d ₃₃ (pm / V). ◆ The mark indicates the firing temperature of 1000 ℃, the mark shows the firing temperature of 975 ℃, and the mark indicates the firing temperature of 950 ℃.

As apparent from Table 3 and FIG. 3, it was confirmed that the piezoelectric constant (d ₃₃ ) also tended to increase as the content of WO ₃ increased and the firing temperature was lower.

Claims (6)

A multilayer piezoelectric element having an element in which an internal electrode layer and a piezoelectric ceramic layer are alternately stacked, The internal electrode layer has Cu as a main component, and the piezoelectric ceramic layer has a composite oxide represented by Pb (Ti, Zr) O ₃ as a main component, And a metal oxide containing at least one of a pentavalent and six-valent metal element is contained in the piezoelectric ceramic layer so that its concentration becomes lower as it is separated from the internal electrode layer. The multilayer piezoelectric element of claim 1, wherein the metal element is at least one selected from Nb, Sb, Ta, and W. 3. A lamination type piezoelectric method including a lamination process of manufacturing a laminate in which internal electrode patterns and piezoelectric ceramic green sheets are alternately laminated, and a firing process of firing the laminate to produce a body in which internal electrode layers and piezoelectric ceramic layers are alternately laminated. As a manufacturing method of the device, The piezoelectric ceramic green sheet has a composite oxide represented by Pb (Ti, Zr) 0 ₃ as a main component, The internal electrode pattern includes a conductive powder containing Cu and a metal element having a valence number of at least one of pentavalent and hexavalent, In the firing step, the metal element is diffused in the form of a metal oxide in the piezoelectric ceramic layer from the inner electrode layer, so that the concentration is lowered as it is separated from the inner electrode layer. 4. The method of claim 3, wherein the metal element is at least one selected from Nb, Sb, Ta, and W. 5. 5. The method of claim 3, wherein the metal oxide is represented by any one of Nb ₂ O ₅ , Sb ₂ O ₅ , Ta ₂ O _5, and WO _{3. 6} . The method of manufacturing a laminated piezoelectric element according to any one of claims 3 to 5, wherein the content of the metal oxide is less than 40.0% by weight based on the total amount of the conductive powder and the metal oxide.

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